The present invention relates to a one-way clutch which allows a rotary member to be rotated in a direction but prevents the member from being rotated in another direction.
There is a conventional one-way clutch comprising an outer race 1", an inner race 10, a retainer 2", and a plurality of slender cylindrical rollers 3" housed in the retainer between the outer and the inner races, as shown in FIGS. 14 and 15. The clutch allows a rotary member to be rotated in a direction but prevents the member from being rotated in another direction. The movement of the rollers 3" for a wedge effect at the time of the backward rotation of the clutch is small. The clutch can be easily fitted between the rotary member and a support member. The outer race 1" is made of a cement steel plate high enough in strength against the wedge effect between the outer race and the rollers 3" and is cylindrically shaped so that the outer race has an end portion extending in the radial direction of the race, a plurality of peripheral projections 1e each slenderly extending between both the ends of the race, recesses 1f formed inside the projections, inner sloped 1g formed inside the projections, and a through hole 1h formed inside the end portion so as to fit the inner race 10 in the hole. The outer race 1" is thereafter subjected to nitriding and anticorrosive processing. After the retainer 2" is put in the outer race 1", the race is bend at one end thereof to have another end portion 1i for keeping the retainer from coming out the outer race.
Since the outer race 1" has a relatively complicated form, there are problems that the race is expensive and it is difficult to keep the accuracy of the form of each of the recesses 1f and the slopes 1g high enough to stabilize the function of the clutch. The axial dimension of each of the rollers 3" is large, while the outside diameter of the roller is small. When the outside diameter of the inner race 10 is small and the one-way clutch is included in a device whose rotational frequency at the clutch is low, no trouble takes place. However, when the inner race 10 is large in outside diameter and small in axial dimension and the clutch is included in a device whose rotational frequency at the clutch is high, troubles (1), (2) and (3) take place as follows:
(1) If the axial dimension of each of the slender cylindrical rollers is decreased for weight reduction or other purpose without changing the outside diameter of the roller, the pressure on the surface of he roller is heightened to make it likely that the roller is pressed onto the inner or outer race and locked thereon due to a rotative impact, or local flawing, deformation, wear or the like is accelerated.
(2) If the number of the rollers, which roll in slipping pressure contact with the inner race, is large, the power for rotating the clutch needs to be high. If the number of the rollers is small, the transmissible torque of the clutch is lowered in proportion to the number.
(3) If the outer race of the clutch, whose inner race is usually rotated at a high speed for the rapid rotation of the device, is rotated at a high speed for that purpose, the rollers are separated from the inner race due to a centrifugal force so as to delay the action of the clutch.